It is known to electrically couple multiple switching subconverters in parallel to increase switching power converter capacity and/or to improve switching power converter performance. A multi-phase switching power converter typically performs better than a single-phase switching power converter of otherwise similar design. In particular, the out-of-phase switching in a multi-phase converter results in ripple current cancellation at the converter output filter and allows the multi-phase converter to have a better transient response than an otherwise similar single-phase converter.
As taught in U.S. Pat. No. 6,362,986 to Schultz et al., which is incorporated herein by reference, a multi-phase switching power converter's performance can be improved by magnetically coupling the energy storage inductors of two or more phases. Such magnetic coupling results in ripple current cancellation in the inductors and increases ripple switching frequency, thereby improving converter transient response, reducing input and output filtering requirements, and/or improving converter efficiency, relative to an otherwise identical converter without magnetically coupled inductors.
Two or more magnetically coupled inductors are often collectively referred to as a “coupled inductor” and have associated leakage inductance and magnetizing inductance values. Magnetizing inductance is associated with magnetic coupling between windings; thus, the larger the magnetizing inductance, the stronger the magnetic coupling between windings. Leakage inductance, on the other hand, is associated with energy storage. Thus, the larger the leakage inductance, the more energy stored in the inductor. As taught in Schultz et al., larger magnetizing inductance values are desirable to better realize the advantages of using a coupled inductor, instead of discrete inductors, in a switching power converter. Leakage inductance, on the other hand, typically must be within a relatively small value range. In particular, leakage inductance must be sufficiently large to prevent excessive ripple current magnitude, but not so large that converter transient response suffers.